Radial piston hydraulic motor of variable cylinder capacity

Abstract

In a radial piston hydraulic motor of the "star-shaped" type the variation of the cylinder capacity is achieved by the fact that the motor crankshaft is provided with a mechanism which varies the eccentricity, this mechanism being powered by hydraulic actuators carried by the shaft and controlled by a circuit external to the frame of the motor, comprising a rotating coupling and stop valves, while stability of the cylinder capacity may be obtained by means of locking mechanisms carried on the shaft.

I claim: 
     
       1. A hydraulic motor, comprising: a housing;   a shaft journaled in said housing and rotatable about an axis of rotation;   means in said housing forming a plurality of radial cylinders angularly spaced around said shaft;   respective drive pistons reciprocatable in said cylinders and having inner ends turned toward said shaft;   a ring of circular outer periphery surrounding said shaft and interposed between said shaft and said inner ends, said inner ends bearing on said ring, said ring and said shaft having confronting guide surfaces respectively along an interior of said ring and an exterior of said shaft enabling said ring to shift radially on said shaft and thereby vary an eccentricity of said outer periphery of said ring with respect to said shaft;   piston means displaceable in said shaft and surrounded by said ring for displacing said ring radially relative to said shaft to set said eccentricity and thereby vary a capacity of said cylinders; and   controllable locking means releasably securing said ring to said shaft at an eccentricity set by said piston means and disengageable for resetting of said eccentricity, said shaft being provided with an engaging element mounted rotatably fixed in said shaft, said controllable locking means including surfaces on said ring and said engaging element provided with respective pluralities of longitudinal teeth parallel to said axis of rotation of said shaft and automatically meshing with one another to prevent radial shifting of said ring by pressure of said drive pistons thereagainst, and hydraulic means for relieving pressing of said pluralities of teeth against one another to enable displacement of said ring by said piston means.   
     
     
       2. The motor defined in claim 1 wherein said engaging element is a pawl provided with: a first flank formed with the respective plurality of teeth,   a second flank parallel to said first flank and forming an inner chamber with said shaft and an outer chamber with said interior of the ring, said inner chamber communicating with said hydraulic means, and   a bridging part connecting said flanks, so that said pawl has an "H" cross section, said shaft being formed with an undercut portion extending radially outwardly from said bridging part and forming a compartment with said first flank and with said bridging part of the pawl.   
     
     
       3. The motor defined in claim 2, further comprising a spring mounted in said compartment and generating a radial outward thrust against said first flank of the pawl ensuring thereby the locking position of said ring and said shaft, said pawl being displaced diametrically opposite to said radial thrust produced by said spring into said outer chamber upon receiving a hydraulic media by said inner chamber. 
     
     
       4. A hydraulic motor of a rotary type with variable cylinder capacity, comprising: a motor frame;   a motor shaft journaled in said frame and rotatable about an axis of rotation and provided with an engaging element mounted rotatably fixed in said shaft and provided with a plurality of longitudinal teeth extending parallel to said axis of rotation;   an eccentric ring mounted on and rotationally coupled to said shaft;   hydraulic actuators carried by the shaft;   a rotating hydraulic coupling, caused to rotate by the shaft and connecting said actuators to a control circuit, said rotating coupling being integral with and external to the frame of the motor and connected hydraulically to the said actuators by means of elements which rotate with the shaft;   drive pistons radially shiftable in respective drive cylinders on said frame and bearing radially on said ring for driving said shaft; and   a distributor for activating said drive pistons, said actuators comprising positioning pistons which slide in corresponding positioning cylinders in said ring, said ring being formed with a respective surface provided with a respective plurality of ring teeth meshing with said plurality of teeth of said engaging element forming locking means for preventing arbitrary radial shifting of said ring and for release upon actuation of said positioning pistons so that said ring is radially guided transversely to said axis of rotation, said ring being radially locked with respect to the axis of rotation by the locking means which can be relieved in a controlled way through said rotating hydraulic coupling.   
     
     
       5. A motor as defined in claim 4 wherein said engaging element is a locking pawl. 
     
     
       6. A motor as defined in claim 5 wherein a hydraulic locking of said ring is achieved by means of small pistons whose respective cylinders are hydraulically connected through means which pass through the center of the distributor operatively connected with stop valves which rotate with the shaft and are supplied through said rotating hydraulic coupling.